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Anorganic ChemistryMolecular Orbital TheoryDeta Rispa Dini06111410015

Chemistry Education Study ProgramFaculty Of Teacher and Training Education CenterSriwijaya University2014IntroductionMolecular Orbital DiagramMolecular Orbitals Of ComplexesConclusionsVideoA. Introduction The goal of molecular orbital theory is to describe molecules in a similar way to how we describe atoms, that is, in terms of orbitals, orbital diagrams, and electron configurations. Molecular orbitals result from the combination of atomic orbitals. Since orbitals are wave functions, they can combine either constructively (forming a bonding molecular orbital), or destructively (forming an antibonding molecular orbital).Molecular orbitals form when atomic orbitals with similar energies and proper symmetry can overlap. Atomic orbitals with differing energies or the wrong spatial orientation (orthogonal) do not combine, and are called non-bonding orbitals.Constructively:() or + = (1/2 ) [(1sa) + (1sb) ]

Destructively:(*) or - = (1/2 ) [(1sa) - (1sb) ]Molecular Orbital TheoryMolecular Orbital TheoryThe bonding orbital results in increased electron density between the two nuclei, and is of lower energy than the two separate atomic orbitals.

5Molecular Orbital TheoryThe bonding orbital is sometimes given the notation g, where the g stands for gerade, or symmetric with respect to a center of inversion.

++-The signs on the molecular orbitals indicate the sign of the wave function, not ionic charge.Molecular Orbital TheoryThe anti-bonding orbital is sometimes given the notation u, where the u stands for ungerade, or asymmetric with respect to a center of inversion.

++-The signs on the molecular orbitals indicate the sign of the wave function, not ionic charge.Molecular Orbital DiagramThis is a molecular orbital energy level diagram for the p orbitals. Note that the bonding orbital is lowest in energy due to the greater overlap end-on-end.

2p2pguguMolecular Orbital DiagramThe alternate notation is provided on the right side of the energy level diagram.

2p2pguguMolecular Orbital DiagramsElectrons preferentially occupy molecular orbitals that are lower in energy.Molecular orbitals may be empty, or contain one or two electrons.If two electrons occupy the same molecular orbital, they must be spin paired.When occupying degenerate molecular orbitals, electrons occupy separate orbitals with parallel spins before pairing.Molecular Orbital DiagramsAlthough molecular orbitals form from inner (core) electrons as well as valence electrons, many molecular orbital diagrams include only the valence level.Molecular Orbital Diagrams

For O2, there will be a total of 12 valence electrons that must be placed in the diagram.Molecular Orbital DiagramsFor O2, there will be a total of 12 valence electrons that must be placed in the diagram.

2p2p2s2sMolecular Orbital DiagramsFor O2, there will be a total of 12 valence electrons that must be placed in the diagram.

2p2p2s2sMolecular Orbital TheoryEach line in the diagram represents an orbital.The molecular orbital volume encompasses the whole molecule.The electrons fill the molecular orbitals of molecules like electrons fill atomic orbitals in atomsMolecular Orbital TheoryElectrons go into the lowest energy orbital available to form lowest potential energy for the molecule.The maximum number of electrons in each molecular orbital is two. (Pauli exclusion principle) One electron goes into orbitals of equal energy, with parallel spin, before they begin to pair up. (Hund's Rule.) Molecular Orbital Diagram (H2)

http://www.ch.ic.ac.uk/vchemlib/course/mo_theory/main.htmlMO Diagram for O2http://www.chem.uncc.edu/faculty/murphy/1251/slides/C19b/sld027.htm

Molecular Orbital Diagram (HF)

http://www.ch.ic.ac.uk/vchemlib/course/mo_theory/main.htmlMolecular Orbital Diagram (CH4)So far, we have only look at molecules with two atoms.MO diagrams can also be used for larger molecules.

http://www.ch.ic.ac.uk/vchemlib/course/mo_theory/main.htmlMolecular Orbital Diagram (H2O)

Molecular Orbitals of ComplexesGroup theory is also used to construct molecular orbital diagrams for the complexes of metal atoms or ions. The symmetry combinations of the atomic orbitals on the ligands are determined, and then matched with appropriate atomic orbitals on the central metal. Both and bonding between the metal and ligands can be considered.ConclusionsBonding electrons are localized between atoms (or are lone pairs).Atomic orbitals overlap to form bonds.Two electrons of opposite spin can occupy the overlapping orbitals.Bonding increases the probability of finding electrons in between atoms.It is also possible for atoms to form ionic and metallic bonds.VIDEO